A single-phase photovoltaic storage and Vv connection traction transformer coordinated power supply system

Abstract

The present application belongs to the technical field of electrified railway traction power supply, and particularly relates to a single-phase and Vv connection traction transformer coordinated power supply system containing photovoltaic storage. In the present application, the traction power supply system realizes the switching of the same-phase photovoltaic storage power supply mode and the different-phase photovoltaic storage power supply mode by controlling the opening and closing of the circuit breaker group QF and the disconnector QS; when the influence of the single-phase traction load on the power system meets the national standard requirements, the same-phase photovoltaic storage power supply mode is realized by the single-phase connection traction transformer; when the power system is weak and the large-density trains are running, the influence of the single-phase traction load on the power system exceeds the national standard limit, and the two single-phase connection traction transformers realize Vv connection, and the different-phase photovoltaic storage power supply mode is realized by the Vv connection traction transformer. The present application is helpful for the nearby consumption of photovoltaic, the recycling of regenerative braking energy, and the improvement of the power quality problem mainly caused by negative sequence, and is particularly suitable for the transformation of the Vv connection or Vx connection traction substation widely used in the current high-speed railway and passenger dedicated line.

Description

Technical Field

[0001] This invention belongs to the field of electrified railway traction power supply technology, specifically relating to a single-phase and Vv-connected traction transformer power supply system with photovoltaic energy storage. Background Technology

[0002] Electrified railways are one of the major electricity consumers in the power system. Every year, the railway department pays a large amount of electricity fees to the power sector. If new energy sources such as photovoltaic and wind power can be connected to the traction power supply system for traction grid power supply, it can not only save a lot of electricity fees, but also increase the proportion of clean energy in the energy consumption of the traction power supply system, which is in line with the national development direction of energy conservation and emission reduction.

[0003] Traction loads are characterized by significant fluctuations, with a large difference between peak and trough power values. During normal operation, traction transformers are mostly underloaded, while overload occurs during short periods of intensive operation, resulting in average power far below maximum power. This leads to excessively large installed capacity of traction transformers and low utilization of traction power supply equipment. Furthermore, electric locomotives, operating under regenerative braking, feed energy back into the power system. Proper utilization of this energy can effectively reduce railway power consumption. Energy storage devices possess the dual characteristics of energy storage and release, effectively absorbing regenerative braking energy. They can discharge during peak loads and recharge during off-peak loads, mitigating traction load fluctuations and alleviating the pressure of peak power on the system and equipment.

[0004] Therefore, researching how to efficiently connect energy storage and photovoltaics into the traction power supply system is beneficial to promoting the local consumption of photovoltaics and the recycling and utilization of renewable energy, as well as improving the power quality problem dominated by negative sequence. Summary of the Invention

[0005] The purpose of this invention is to provide a single-phase and Vv-connected traction transformer power supply system that integrates photovoltaic and energy storage, enabling power dispatching between power supply arms; it is beneficial for photovoltaic absorption and the recovery and utilization of regenerative braking energy, and improves the power quality problem dominated by negative sequence.

[0006] The technical solution adopted in this invention is:

[0007] A single-phase and Vv-connected traction transformer coordinated power supply system incorporating photovoltaic and energy storage includes a first single-phase traction transformer, a second single-phase traction transformer, a first power supply arm, and a second power supply arm. It also includes a first converter, a second converter, a first isolation transformer, a second isolation transformer, a photovoltaic unit, an energy storage unit, and a measurement and control unit. The primary side of the first single-phase traction transformer is connected to phases A and C of a three-phase high-voltage busbar via a first circuit breaker QF1 and a second circuit breaker QF2, respectively. One end of the secondary side of the first single-phase traction transformer is connected to the first... The primary side of the second single-phase traction transformer is connected to phases B and C of the three-phase high-voltage bus via circuit breakers QF3 and QF4, respectively. One end of the secondary side of the second single-phase traction transformer is connected to the second traction bus via circuit breaker QF6. The other end of the secondary side of the first single-phase traction transformer is grounded and connected to the other end of the secondary side of the second single-phase traction transformer via disconnector QS1. The other end of the secondary side of the first single-phase traction transformer and the other end of the secondary side of the second single-phase traction transformer are in phase.

[0008] A first voltage transformer VT1 is installed on the first traction bus, and a second voltage transformer VT2 is installed on the second traction bus. The first traction bus is connected to one end of the primary winding of the first isolation transformer through the seventh circuit breaker QF7. The other end of the primary winding of the first isolation transformer is grounded. The secondary winding of the first isolation transformer is connected to the AC terminal of the first converter. A first inductance exists between one end of the secondary winding of the first isolation transformer and one end of the AC terminal of the first converter. The second traction bus is connected to one end of the primary winding of the second isolation transformer through the eighth circuit breaker QF8. The other end of the primary winding of the second isolation transformer is grounded. The secondary winding of the second isolation transformer is connected to the AC terminal of the second converter. A second inductance exists between one end of the secondary winding of the second isolation transformer and one end of the AC terminal of the second converter.

[0009] A third current transformer CT3 is also installed between the seventh circuit breaker QF7 and one end of the primary winding of the first isolation transformer; a fourth current transformer CT4 is also installed between the eighth circuit breaker QF8 and one end of the primary winding of the second isolation transformer; the connection terminals of the seventh circuit breaker QF7 and the third current transformer CT3 are connected to the connection terminals of the eighth circuit breaker QF8 and the fourth current transformer CT4 through the twelfth circuit breaker QF12.

[0010] The solar energy unit and the energy storage unit are connected to the DC side of the first converter and the second converter respectively through DC / DC converters;

[0011] The first traction busbar is connected to the first power supply arm via the ninth circuit breaker QF9. The first traction busbar is also connected to the second power supply arm via the eleventh circuit breaker QF11. A first current transformer CT1 is also installed between the ninth circuit breaker QF9, the eleventh circuit breaker QF11 and the first traction busbar. The second traction busbar is connected to the second power supply arm via the tenth circuit breaker QF10. A second current transformer CT2 is also installed between the tenth circuit breaker QF10 and the second power supply arm.

[0012] An electrical phase separation is provided between the first power supply arm and the second power supply arm, which are connected by the second disconnect switch QS2 and the third disconnect switch QS3 respectively.

[0013] The input to the measurement and control unit is the measurement signals from the first current transformer CT1, the second current transformer CT2, the third current transformer CT3, the fourth current transformer CT4, the first voltage transformer VT1, and the second voltage transformer VT2. The output of the measurement and control unit is connected to the control terminals of all circuit breakers and disconnectors. The measurement and control unit is used to control the opening and closing of circuit breakers and disconnectors based on the obtained measurement signals to achieve the switching between in-phase and out-of-phase photovoltaic-storage power supply modes. The specific control method is as follows:

[0014] When the impact of a single-phase traction load on the power system meets national standards, the single-phase traction transformer achieves a same-phase photovoltaic-storage power supply mode. Specifically, the first circuit breaker QF1, the second circuit breaker QF2, and the fifth circuit breaker QF5 are closed, the third circuit breaker QF3, the fourth circuit breaker QF4, and the sixth circuit breaker QF6 are open, and the first disconnecting switch QS1 is open. At this time, the second single-phase traction transformer does not work, and the first single-phase traction transformer draws power from the grid independently. The ninth circuit breaker QF9 and the eleventh circuit breaker QF11 are closed, and the tenth circuit breaker... When circuit breaker QF10 is disconnected, the second isolating switch QS2 and the third isolating switch QS3 are closed. At this time, both the first and second power supply arms draw power from the first traction bus and there is no phase separation. When circuit breaker QF8 is disconnected, the seventh circuit breaker QF7 and the twelfth circuit breaker QF12 are closed. At this time, the output ports of the first and second converters are connected in parallel to the first traction bus. When the traction network is unloaded or lightly loaded, the solar energy unit charges the energy storage unit to store energy. When the traction network is heavily loaded, the energy storage unit releases energy and supplies power to the traction load together with the solar energy unit.

[0015] When the impact of a single-phase traction load on the power system exceeds the national standard limit, the two single-phase traction transformers are connected in a Vv configuration. The Vv-connected traction transformers then implement an out-of-phase photovoltaic-storage power supply mode. Specifically, the first circuit breaker QF1, the second circuit breaker QF2, the third circuit breaker QF3, the fourth circuit breaker QF4, the fifth circuit breaker QF5, and the sixth circuit breaker QF6 are closed, and the first disconnecting switch QS1 is closed. At this time, the first and second single-phase traction transformers form a Vv-connected traction transformer that draws power from the grid together; the ninth circuit breaker QF9 and the tenth circuit breaker QF10 are closed, and the eleventh... When circuit breaker QF11 is open, and the second disconnecting switch QS2 and the third disconnecting switch QS3 are open, the first power supply arm draws power from the first traction bus, and the second power supply arm draws power from the second traction bus. There is a phase separation between the first power supply arm and the second power supply arm. When the seventh circuit breaker QF7 and the eighth circuit breaker QF8 are closed, and the twelfth circuit breaker QF12 is open, the output ports of the first converter and the second converter are connected to the first traction bus and the second traction bus, respectively. At this time, the traction load is powered by the energy storage unit, the solar energy unit, the first single-phase traction transformer and the second single-phase traction transformer.

[0016] The beneficial effects of this invention are as follows: This invention provides a structure for a single-phase and Vv-connected traction transformer power supply system with photovoltaic and energy storage. The switching between in-phase and out-of-phase photovoltaic and energy storage power supply modes can be achieved by controlling the opening and closing of the circuit breaker group QF and the disconnecting switch QS. This helps to facilitate the local consumption of photovoltaic power, the recovery and utilization of regenerative braking energy, and improve the power quality problem dominated by negative sequence. It is especially suitable for the renovation of Vv-connected or Vx-connected traction substations that are currently widely used in high-speed railways and passenger dedicated lines. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the construction of a single-phase power supply system with photovoltaic energy storage and Vv-connected traction transformers, which is used in an embodiment.

[0018] Figure 2 This is a connection diagram of the present invention for an AT traction power supply system of 2-27.5kV. Detailed Implementation

[0019] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0020] Example

[0021] like Figure 1As shown, the power supply system in this example includes a three-phase high-voltage bus, two single-phase traction transformers, phase a traction bus, phase b traction bus, grounding bus, power regulation unit, photovoltaic unit, energy storage unit, and measurement and control unit. The system consists of two single-phase traction transformers, TT1 and TT2. TT1 is connected to one phase high-voltage bus (phase AB in this example), and TT2 is connected to the other phase high-voltage bus (phase CB in this example). The terminals of the same phase on the secondary side of TT1 and TT2 are connected to the grounding bus through a disconnecting switch QS1. The terminals of two different phases on the secondary side of TT1 and TT2 (phase A terminal of TT1 and phase C terminal of TT2 in this example) are connected to the two traction buses (phase a traction bus and phase b traction bus in this example) through circuit breakers. Select one traction bus as the main power supply bus (connected to phase a traction bus in this example), and lead two feeders to the left power supply arm a and the right power supply arm b respectively. These two feeders consist of disconnecting switches and circuit breaker groups (circuit breaker groups QF9 and QF11 are used in this example), and are equipped with current transformers CT1. They can operate in either 100% or 50% standby mode. Another feeder is led from the other traction bus (connected to traction bus b in this example) to the right power supply arm b. This feeder also consists of disconnecting switches and circuit breaker groups (circuit breaker group QF10 is used in this example), and is equipped with current transformers CT2. The circuit breakers operate in 100% standby mode. Voltage transformers VT1 are installed on phase a traction bus, and voltage transformers VT2 are installed on phase b traction bus. A phase separation circuit is established between power supply arms a and b, connected by disconnecting switches QS2 and QS3. The power regulation unit includes a phase a converter and a phase b converter arranged symmetrically. The AC terminal of the phase a converter is connected to a traction bus (in this example, traction bus a) by a feeder line led out from the left inductor L1 and the left isolation transformer TT3. This feeder line is composed of a circuit breaker group (in this example, a circuit breaker group QF7 is used) and a current transformer CT3 is installed on it. The AC terminal of the b-side converter is connected to two feeders via the right-side inductor L2 and the right-side isolation transformer TT4, respectively, to traction bus a and traction bus b. The two feeders are composed of circuit breaker groups (QF12 and QF8 groups are used in this example) and are equipped with current transformers CT4. The photovoltaic unit and energy storage unit are connected to the DC side between the a-phase converter and the b-phase converter via DC / DC converters. The measurement terminal of the measurement and control unit is connected to the measurement signal output terminals of current transformers CT1, CT2, CT3, CT4, VT1, and VT2, respectively. The output terminal of the measurement and control unit is connected to the control terminal of the power regulation unit and each circuit breaker group.

[0022] The traction power supply system switches between in-phase and out-of-phase photovoltaic-storage power supply modes by controlling the opening and closing of circuit breaker group QF and disconnector switch QS.

[0023] When the impact of a single-phase traction load on the power system meets national standards, the same-phase photovoltaic-storage power supply mode is achieved by a single-phase traction transformer. Circuit breaker groups QF1, QF2, and QF5 are closed, QF3, QF4, and QF6 are open, and disconnector switch QS1 is open. At this time, traction transformer TT2 is not working, and traction transformer TT1 draws power from the grid independently. Circuit breaker groups QF9 and QF11 are closed, QF10 is open, and disconnectors QS2 and QS3 are closed. At this time, both power supply arms a and b draw power from traction bus a, and there is no phase separation. Circuit breaker group QF8 is open, and QF7 and QF12 are closed. At this time, the output ports on sides a and b of the power regulation unit are connected in parallel to the traction bus of phase a. When the traction network is unloaded or lightly loaded, the photovoltaic unit charges and stores energy for the energy storage unit. When the traction network is heavily loaded, the energy storage unit releases energy, working together with the photovoltaic unit to supply power to the traction load. When the output power of the photovoltaic unit is low or the load on the traction network is too high, the switching of the phased photovoltaic-storage power supply mode is achieved by controlling the opening and closing of the circuit breaker group.

[0024] When the power system is weak and there is high-density traffic, and the impact of single-phase traction load on the power system exceeds the national standard limit, two single-phase traction transformers are connected in a Vv configuration, and the Vv-connected traction transformers achieve a different-phase photovoltaic-storage power supply mode. Circuit breaker groups QF1, QF2, QF3, QF4, QF5, and QF6 are closed, and disconnector switch QS1 is closed; at this time, traction transformers TT1 and TT2 form a Vv-connected traction transformer that draws power from the grid together; circuit breaker groups QF9 and QF10 are closed, QF11 is open, and disconnectors QS2 and QS3 are open; at this time, power supply arm a draws power from the a-phase traction bus, and power supply arm b draws power from the b-phase traction bus, with electrical phase separation between power supply arm a and power supply arm b; circuit breaker groups QF7 and QF8 are closed, and QF12 is open; at this time, the a-side output port and the b-side output port of the power regulation unit are connected to the a-phase traction bus and the b-phase traction bus, respectively. At this time, the traction load is powered by the energy storage unit, the photovoltaic power supply unit, the traction transformer TT1, and the traction transformer TT2.

[0025] Figure 2 This is a connection diagram of the present invention used in an AT traction power supply system, wherein the connection method of the high-voltage bus is similar to... Figure 1Similarly, under AT power supply mode, the midpoints of the secondary windings of traction transformers TT1 and TT2, and isolation transformers TT3 and TT4 are all grounded, with a voltage of 2×27.5kV. In the diagram, QF1, QF2, QF3, QF4, QF5, QF6, QF7, QF8, QF9, QF10, QF11, QF12, QF13, QF14, QF15, QF16, QF17, and QF18 are circuit breaker groups; QS1, QS2, QS3, QS4, and QS5 are disconnect switches; CT1, CT2, CT3, CT4, CT5, CT6, CT7, and CT8 are current transformers; and VT1, VT2, VT3, and VT4 are voltage transformers.

Claims

1. A single-phase and Vv-connected traction transformer coordinated power supply system incorporating photovoltaic energy storage, comprising a first single-phase connected traction transformer, a second single-phase connected traction transformer, a first power supply arm, and a second power supply arm, characterized in that, It also includes a first converter, a second converter, a first isolation transformer, a second isolation transformer, a solar energy unit, an energy storage unit, and a measurement and control unit; the primary side of the first single-phase traction transformer is connected to phase A and phase C of the three-phase high-voltage bus via the first circuit breaker QF1 and the second circuit breaker QF2, respectively, and one end of the secondary side of the first single-phase traction transformer is connected to the first traction bus via the fifth circuit breaker QF5; the primary side of the second single-phase traction transformer is connected to phase B and phase C of the three-phase high-voltage bus via the third circuit breaker QF3 and the fourth circuit breaker QF4, respectively, and one end of the secondary side of the second single-phase traction transformer is connected to the second traction bus via the sixth circuit breaker QF6; the other end of the secondary side of the first single-phase traction transformer is grounded and also connected to the other end of the secondary side of the second single-phase traction transformer via the first disconnecting switch QS1, and the other end of the secondary side of the first single-phase traction transformer and the other end of the secondary side of the second single-phase traction transformer are in phase. A first voltage transformer VT1 is installed on the first traction bus, and a second voltage transformer VT2 is installed on the second traction bus. The first traction bus is connected to one end of the primary winding of the first isolation transformer through the seventh circuit breaker QF7. The other end of the primary winding of the first isolation transformer is grounded. The secondary winding of the first isolation transformer is connected to the AC terminal of the first converter. A first inductance exists between one end of the secondary winding of the first isolation transformer and one end of the AC terminal of the first converter. The second traction bus is connected to one end of the primary winding of the second isolation transformer through the eighth circuit breaker QF8. The other end of the primary winding of the second isolation transformer is grounded. The secondary winding of the second isolation transformer is connected to the AC terminal of the second converter. A second inductance exists between one end of the secondary winding of the second isolation transformer and one end of the AC terminal of the second converter. A third current transformer CT3 is also installed between the seventh circuit breaker QF7 and one end of the primary winding of the first isolation transformer; a fourth current transformer CT4 is also installed between the eighth circuit breaker QF8 and one end of the primary winding of the second isolation transformer; the connection terminals of the seventh circuit breaker QF7 and the third current transformer CT3 are connected to the connection terminals of the eighth circuit breaker QF8 and the fourth current transformer CT4 through the twelfth circuit breaker QF12. The solar energy unit and the energy storage unit are connected to the DC side of the first converter and the second converter respectively through DC / DC converters; The first traction busbar is connected to the first power supply arm via the ninth circuit breaker QF9. The first traction busbar is also connected to the second power supply arm via the eleventh circuit breaker QF11. A first current transformer CT1 is also installed between the ninth circuit breaker QF9, the eleventh circuit breaker QF11 and the first traction busbar. The second traction busbar is connected to the second power supply arm via the tenth circuit breaker QF10. A second current transformer CT2 is also installed between the tenth circuit breaker QF10 and the second power supply arm. An electrical phase separation is provided between the first power supply arm and the second power supply arm, which are connected by the second disconnect switch QS2 and the third disconnect switch QS3 respectively. The input to the measurement and control unit is the measurement signals from the first current transformer CT1, the second current transformer CT2, the third current transformer CT3, the fourth current transformer CT4, the first voltage transformer VT1, and the second voltage transformer VT2. The output of the measurement and control unit is connected to the control terminals of all circuit breakers and disconnectors. The measurement and control unit is used to control the opening and closing of circuit breakers and disconnectors based on the obtained measurement signals to achieve the switching between in-phase and out-of-phase photovoltaic-storage power supply modes. The specific control method is as follows: When the impact of a single-phase traction load on the power system meets national standards, the single-phase traction transformer achieves a same-phase photovoltaic-storage power supply mode. Specifically, the first circuit breaker QF1, the second circuit breaker QF2, and the fifth circuit breaker QF5 are closed, the third circuit breaker QF3, the fourth circuit breaker QF4, and the sixth circuit breaker QF6 are open, and the first disconnecting switch QS1 is open. At this time, the second single-phase traction transformer does not work, and the first single-phase traction transformer draws power from the grid independently. The ninth circuit breaker QF9 and the eleventh circuit breaker QF11 are closed, and the tenth circuit breaker... When circuit breaker QF10 is disconnected, the second isolating switch QS2 and the third isolating switch QS3 are closed. At this time, both the first and second power supply arms draw power from the first traction bus and there is no phase separation. When circuit breaker QF8 is disconnected, the seventh circuit breaker QF7 and the twelfth circuit breaker QF12 are closed. At this time, the output ports of the first and second converters are connected in parallel to the first traction bus. When the traction network is unloaded or lightly loaded, the solar energy unit charges the energy storage unit to store energy. When the traction network is heavily loaded, the energy storage unit releases energy and supplies power to the traction load together with the solar energy unit. When the impact of a single-phase traction load on the power system exceeds the national standard limit, the two single-phase traction transformers are connected in a Vv configuration. The Vv-connected traction transformers then implement an out-of-phase photovoltaic-storage power supply mode. Specifically, the first circuit breaker QF1, the second circuit breaker QF2, the third circuit breaker QF3, the fourth circuit breaker QF4, the fifth circuit breaker QF5, and the sixth circuit breaker QF6 are closed, and the first disconnecting switch QS1 is closed. At this time, the first and second single-phase traction transformers form a Vv-connected traction transformer that draws power from the grid together; the ninth circuit breaker QF9 and the tenth circuit breaker QF10 are closed, and the eleventh... When circuit breaker QF11 is open, and the second disconnecting switch QS2 and the third disconnecting switch QS3 are open, the first power supply arm draws power from the first traction bus, and the second power supply arm draws power from the second traction bus. There is a phase separation between the first power supply arm and the second power supply arm. When the seventh circuit breaker QF7 and the eighth circuit breaker QF8 are closed, and the twelfth circuit breaker QF12 is open, the output ports of the first converter and the second converter are connected to the first traction bus and the second traction bus, respectively. At this time, the traction load is powered by the energy storage unit, the solar energy unit, the first single-phase traction transformer and the second single-phase traction transformer.

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